Unity3D particle emitter "one shot" tick but still not working?

Okay, So I am playing with the unity particle emitter, and some of the emitter even if you tick "one shot" it still boom over and over again

below is how i fix this

in your shooting script, by default is as below
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Instantiate(explosionPrefab, pos, rot);


Change it to as below
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var haha : Transform;
haha= Instantiate(explosionPrefab, pos, rot);
haha.particleEmitter.Emit();


 Now it should only emit once